1. Field of the Invention
The present invention relates to Ethernet technologies, and in particular, to a method, apparatus and system for ring protection.
2. Description of the Related Art
With the rapid development of the carrier-class Ethernet, the Ethernet Ring Protection (ERP) becomes an Ethernet service protection method that attracts wide attention in the industry. Based on a physical or logical ring topology, the ERP uses a closed loop and Ethernet features to achieve fast protection switching for point-to-point, point-to-multipoint, and multipoint-to-multipoint services. The ERP is characterized by high utilization ratio of bandwidth, high speed of protection switching, low cost of network construction, and support of point-to-multipoint and multipoint-to-multipoint service switching.
The Ethernet ring network uses a ring topology on the link layer. In order to prevent routing a packet as an infinite loop on an Ethernet ring, a blocked port is set on the link layer. When the service packet passes through the blocked port, the blocked port discards the packet. Generally, the same physical topology may correspond to multiple ring instances, and each ring instance has a corresponding blocked port. A ring instance may correspond to a control Virtual Local Area Network (VLAN) and one or a group of service VLAN(s). It should be noted that, the control VLAN is generally used to transmit the control messages of ring instances, and the blocked port does not block the packet and traffic on the control VLAN. FIG. 1 shows an Ethernet ring network in the prior art. As shown in FIG. 1, nodes A to F on the ring network are Ethernet bridges. Port 10 of node B is a blocked port. Normally, when a service packet passes through the blocked port, the service packet is discarded by the blocked port. Generally, the node where a blocked port is located is known as a master node.
In a technical solution in conventional art, an Ethernet Operation Administration and Maintenance (OAM) is used to detect link faults and generate fault alarms, and take protection actions according to fault conditions. The specific process is as follows:
A Continuity Check (CC) packet is sent between adjacent nodes on the ring. If no CC packet is received within a specified period, the link is determined as faulty. If a CC packet is received again after fault occurrence, the link is determined as recovering from the fault.
In the technical solutions in the conventional art, the fault detection methods are similar, but the specific protection switching modes are different. The protection switching mode either needs to define new alarm messages, which is incompatible with the existing Ethernet OAM standard, or makes fault recovery scarcely possible in the case of multi-point faults on the Ethernet ring.